There are hundreds of reaction vessels (cuvettes) used on common high-throughput testing apparatus (e.g., clinical analyzers). A patient sample, one or more reagents, and possibly other constituents are delivered into each of the cuvettes, after which a chemical reaction between the one or more reagents and sample takes place in the cuvettes. The mixture of samples, one or more reagents and possibly other constituents undergo incubation and are then read with a read device to determine a characteristic of interest (e.g., an amount of nucleic acid present) in the sample. In some embodiments, where magnetic beads are used, the beads may undergo washing and are subjected to an elution buffer prior to the read. The read device may be a fluorescent or color read device, for example. In some testing apparatus, the cuvettes are automatically washed and then reused.
Although reuse of cuvettes is desirable from a cost standpoint, residual reagent and/or residual sample from a previous test (hereinafter a “donor test”) may be present in a washed cuvette. These residual reagent and/or sample from the “donor test” may possibly interfere with the results of the current test (hereinafter the “recipient test”) when using the washed and reused cuvette. To minimize carryover, the cuvettes are subjected to substantial wash routines in current testing apparatus.
Generally there are two types of cuvette wash routines currently used. The first type of wash routine (hereinafter “default wash”) cleans cuvettes whenever a cuvette is going to be used or when the analyzer has been idle for a certain period of time. There are at least three steps for the default wash that may include: 1) wash with a unique detergent (e.g., a NaOH solution); 2) rinse with water; and 3) drying of the cuvette.
Some reagents are quite difficult to clean off using the default wash, and thus a special type of wash routine (hereinafter “special wash”) may be used to clean cuvettes with special detergents (e.g., acids) wherein the special wash includes: 1) wash with an acid; 2) rinse with water; and 3) drying of the cuvette. Typically, the special wash is followed by a default wash. Sometimes several special wash routines and special detergents are used.
It may take several minutes to complete one wash routine (either default or special) due to system scheduling. For example, if an analyzer has 220 cuvettes resident on board and the system cycle time is three seconds per test, then it will takes about 11 minutes to complete one full wash routine of all cuvettes. It may take 22 minutes or more to clean the cuvettes, if a special wash is performed.
Thus, it should be recognized that these wash routines cause: 1) significant reduction of system throughput, 2) cause significant delay of patient sample testing, and 3) cause delay in obtaining and reporting of the sample results.
One conventional solution to reduce carryover in test apparatus (e.g., clinical analyzers) that use disposable cuvettes is by providing one new cuvette per test. A cuvette loader sub-system may be incorporated to load a new cuvette to the testing apparatus, or other apparatus may be incorporated into the testing apparatus in order to make a new cuvette on the testing apparatus.
Another conventional solution to reduce carryover includes providing in the testing apparatus, two or more identical hardware modules. The donor tests are tested on one module and the recipient tested on the other module.
Although these current methods may mitigate reagent and sample carryover, they may substantially increase system complexity, overall cost, and operating cost. Such complexity may cause reliability issues for the testing apparatus.
Thus, in accordance with one aspect, improved apparatus and methods configured and operable to reduce or eliminate reagent and/or sample carryover are desired.